I’m just seeing this Holo. I do this all the time with Joincopy.
I take all my curve segments, explode any polylines into lines, and put them on a PartA::Control layer. I run those curves through Joincopy, and put the output on a PartA::Crv layer. Then, I group my control curves (after Joincopy, not before).
The join copied curve go on as an input to Revolve, Sweep1, etc., while leaving me able to rebuild any segment to a different degree later.
Sometimes (esp with the Flow commands) it helps to rebuild the PartA::Crv, which you can with -Rebuild pause DeleteInput=No. Then the Joincopy gets hidden on a PartA::Junk layer and the rebuild output moves to PartA::Crv. I do this often where I have a fixed starting and ending crv, with an auto-updating blend in the middle.